Field-Induced Multistate Magnetization Switching in Ferromagnetic Nanowire with Parallel Anti-dots for Memristor Applications

Domain wall (DW)-based devices are attractive for mimicking synaptic behavior, which is fundamental to the realization of neuromorphic computing architecture. Unlike digital electronic devices, it requires analog switching. In this work, we demonstrate the multistate analog switching in a rectangular nanowire with multiple anti-dots using micromagnetic simulations. Anti-dots act as pinning sites for the DW motion during magnetization reversal. The vortex DWs nucleated during the reversal undergo transformation to transverse configuration due to the pinning at the anti-dots. The depinning of the transverse DW takes place in multiple steps. We have also observed the generation of multiple 360° DWs in this structure. The transverse DW breaks into smaller DWs during depinning, leading to stable magnetization states. The number of states achieved directly depends on the number of anti-dots introduced in the nanowire. By introducing six anti-dots, ten stable magnetization states are achieved. The change in demagnetization energy as a function of configuration, shape, and size of the DW is responsible for the observed multistate analog behavior.